IEC 62494-1:2008 specifies definitions and requirements for the exposure index of images acquired with digital X-ray imaging systems. IEC 62494-1:2008 is applicable to digital X-ray imaging systems used in general radiography for producing projection X-ray images for general applications, such as, but not exclusively: - computed radiography (CR) systems based on stimulable phosphors; - flat-panel detector based systems; - charge-coupled device (CCD) based systems. Image intensifier based systems and systems for mammographic or dental application are not covered in this first edition. IEC 62494-1:2008 defines the exposure index only for images generated with a single irradiation event. Images generated from multiple irradiations (e.g., tomosynthetic or dual-energy images, multiple views on a single CR plate) are not covered.